Your problem is that you have already (non-securely) trashed the two items. Thus Nick's excellent advice is more for the future.

I don't know of any way of (a) finding these items and then (b) re-erasing them permanently.

As an extreme measure, I suppose that you could reformat your HD & re-install your OS. But to do this you first need to back up all your folders, photos etc, etc. In my understanding of things — others may advise differently — neither Time Machine nor a Cloning application will do, as there's the theoretical risk of copying back the items from these, after the reformat and re-installation.

Again, in theory, you could just back up all your current folders, data etc to an EHD and the use Migration Assistant to copy these back afterwards. But you would lose all your settings, preferences and so on.

Can it really be worth all of this?

I honestly can't see a practical solution. Sorry. Open to more experienced users to offer more constructive suggestions.